Motor-starter.



M. R. HANNA.

MOTOR STARTER. I APPLI(J ATION FILED SEPT. 12. 1907.

Patented Nov. 30, 1909.

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UNITED STATES MAX R. HANNA, OF SCHENECTADY, NEW YORK, ASSIGNOR TOGENERAL COMPANY, A CORPORATION OF NEW YORK.

PATENT OFFICE.

MOTOR-STARTER.

Specification of Letters Patent.

Patented Nov. 30, 1909.

Application filed September 12, 1907. Serial No. 392,423.

To all whom it may concern:

Be it known that I, MAX R. HANNA, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Motor-Starters, of whichthe following is a specification.

My iifiention relates to motor controllers and: starters andparticularly that type of automatic motor starter in which a number ofelectromagnetic switches or contactors arearranged to close insuccession and short circuit sections of resistance in series with thewhole motor, or in series with its armature.

'Qne well-known type of such control systems is that in which theoperation of the resistance controlling contactors is under the controlof a relay responsive to the current in the motor circuit, which relaycontrols the actuating circuits to the operating coils of thecontactors. Such systems are commonly called current limit controlsystems. These systems of control are extensively used but in someconnections are open to the objection that the overload responsivedevice may not become effective, after the closing of the motor circuit,in time to control the operation of the first resistance controllingcontactor.

Another well-known type of control system, which is particularlyadvantageous, owing to its simplicity, is that in which the actuatingcoils of the resistance controlling cont-actors are arranged in shunt tothe motor or its armature, the contactors being so designed that theywill close one after anpther as the counter electromotiveforce of themotor increases.

;.Such systems are usually referred to as *counter electrometive forcecontrol systems.

' on the motor by a When automatic starting systems of this e are usedin connection with a motor mven from a constant potential source, theymay be made to increase the potential .on the motor by regular andcertain amounts.

If, however, a system of this kind is used.

in connection with a source of current, the potential of which variesconsiderably, the cutting outof the last section of the resistance may.result in increasing the potentlal reater for less amount than desired,depending whether the potential at the source is higher or lower thanthe normal value for which the system was designed. This will' beapparent when it is considered that the operation of the contactorsdepends altogether on the counter clectromotive force of the motor, andis entirely independent of the voltage at the source. All thecontactor-s, except the last one to operate, will, by-cutting out therespective sections of resistance, always increase the voltage on themotor by a certain amount. The contactor which cuts out the last sectionof resistance will, however, when actuated increase the voltage on themotor by an amount which depends upon the voltage at the source. Thatis, if the voltage is higher than normal, the cutting out of the lastsection of resistance will result in suddenly increasing the voltage onthe motor by an amount in excess of the amount intended to be added onthe last step, thereby perhaps overloading the motor while, if thevoltage at the source is below normal, the increase in voltage,resulting from the cutting out of the last section of resistance, may beless than the desired amount, or the last resistance controllingcontactor may fail to close.

An object of my invent-ion is to provide a control system of the type inwhich a plurality of contactors close in succession to increasestep-by-step the voltage applied to the motor irf starting, which willnot be open to the objections mentioned above as usually found incurrent limit and counter clectromotive force control systems. I11 oneaspect my invention may be considered as an improvement on the last asystem of the first mentioned type, since it involves the combination ofthe'principles upon which both types operate.

I have shown my invention as embodied in mi automatic motor starter inwhich the dcred responsive to the counter electromotive force of themotor and the last contactor is prevented from closing until the counterelectromotive force of the 'motor has risen to within a certain amountof the potential at the source or, in other words, until the current inthe motor circuit has ceased to exceed a certain value. Inthe particularembodiment shown, I connect the actuating ,coil of the first resistancecontrolling contactor in shunt to the motor and provide a.

mentioned system, although it may be equally well regar l edanimprovement on first resistance controlling contactor is ren relayhaving its actuating coil connected across a portion of the start ngresistance, the contacts of this relay belng located 1n the controlcircuit through the actuating coil of the last resistance controllingcontactor. This relay is so designed that it will hold its contacts openas long as the fall of potential through the resistance across which itis connected, or, in other words, the

compound wound motor, and I have deemed' it necessary to describe it inconnection with but one of these, since its application to the otherswill be evident to those skilled in the art. It is alsov evident that myinvention is in no way limited to a starter in which there are a,plurality of electro-magnetic switches, since it may equally well beused where but a single contactor cuts'out a single section ofresistance.

Referring to the drawing, Figure 1 is a diagrammatic representation of ashunt motor with an automatic starter applied thereto, in which isembodied my invention, and Fig. 2 is a diagrammatic representation of adynamotor or motor generator provided with an automatic starter of myimproved ty e.

- Eteferring to Fi 1, A represents the armature and F the eld of a shuntmotor. A source of current is shown at T, T with which the motor isconnected by means of a double throw switch S. A starting esistance madeupof two sections R R is arranged in series with the armature, as shown.A conductor 4 serves to connect one terminal of both the armature andfield to the source T, while a conductor connects the other.

source T with the other side of the field and with the resistancearranged in series with the armature. Contactors 6 and 7 are arranged,when actuated, to short circuit the resistances R and R respectively.The actuating coil 8 of the cont-actor 6 is connected on one sidethrough the conductors 9 and at with one terminal of the armature, andon the other side through the conductors 10 and 11 with theotherarmature terminal. The actuating coil 12 of the contactor 7 is similarlyconnected in parallel with the armature A on one side through theconductors 13 and 11, and on the other side by wire 14, fixed contact15, movable contact will not fall until the current passing through ithas been decreased by the reduction to a certain value of the fall ofpotential through the starting resistance, dueto increase in counterelectromotive force in the motor. I

The operation of the system is as follows: \Vhen the switch S is closedcurrent from the source T, T passes in parallel through the field F andthrough the sections of start ing resistance R R and armature A.Armature A then begins to rotate and as its speed increases the counterelectromotive force builds up. l/Vhen this has reached a certain valuesuflicient current will pass through the actuating coil f the contactor6 to operate the same, which will result in short circuiting the sectionof resistance R and increasing the voltage applied to the armature. Thearmature continues to speed up and the counter electromotive forceincreases, but no current can yet pass through the coil 12 of thecontactor 7 since its circuit. is interrupted at the contacts of therelay 18 which pulled up immediately after the switch/S was closed. Thecoil l9-of this relay 18 is now, owing to the closing of the, contactor6, connected in shunt to the section of resistance R and depends for itscurrent on the fall of potential in this sectio n of resistance. Whenthe increasing counter electromotive force of the motor has cut down.the fall of potential through the resistance R to a certain amount, thecurrent through the actuating coil 19 of the relay 18 will beinsufficient td maintain this relay in its raised position and it willdrop thereby bridging the fixed contacts 15 and 17 by the movable.contact 16. Current is now permitted tc' flow through the actuating coil12 of the contactor 7 and the same will be actuated. This results incutting out the last section of resistance R and in increasing thevoltage impressed on the armature By a certain amount.

'In Fig. 2 I have shown my invention as applied to a dynamotor intendedto be used on a railway car or locomotive to reduce the voltage on theline (from say 1200 volts to 600 volts) for use in the auxiliarycircuits of the train. In this figure the motor armature is indicated atA and the generator armature at A while the field, which may be commonto both armatures, is shown at F. The armatures A and A are connectedtogether, as shown, and supply theauxiliary circuit through the leads L,L in a well known manner. The sections of starting resistance R and Rthe" contactors 6 and 7 and the relay 18v are arranged exactly as shownin Fig. 1 above described. Closing of the switch S starts the dynamotorwhich is brought u to speed by the conjunctive operation of e contactors6 and 7 and t e relay 18, as above described in connection with thesystem shown in Fig. 1.

What I. claim as new and desire to secure by Letters Patent of theUnited States, is,.

1. In a motor control system, a motor to be controlled, a plurality ofswitches intended for operation in succession to increase step-by-stepthe voltage applied to the motor in starting, means for ren'derin thefirst switch responsive to the counter e ectromotive force of the motor,and means for rendering the last switch responsive tothe current; in themotor circuit.

- 2: In a motor control system, a motor to be controlled, a plurality ofelectrically controlled switches intended for operation in succession toincrease step-by-step the voltage applied to the motor in starting,means for connecting the actuating coil of the first switch in shunt tothe motor, and means responsive to the current in the motor circuitforcontrolling the energization of theactuuting coil of the last switch.

3. In a motor control system, a motor to be controlled, a startingresistance in the 35 motor circuit, a plurality of electricallycontrolled switches intended for operation in succession to shortcircuit said resistance Section'by section, means for connecting theactuating coil of the firstswitch in shunt to the motor, and a relayhaving its actuating coil connected across a portion of said resistancearranged to control 'the circuit through the actuating coil of the lastswitch wherebysthe same will be prevented fromclosing While the currentin the motor circuit exceeds a certain value. I

rupt the circuit through the actuating coil of the electromagneticswitch while the counter electro-motive force of the motor 15 more thana certain amount below the potential at the source.

5. In combination, a source of current supply, a motorconnectedthereto', a starting resistance for said motor, a plurality ofelectro-magnetic switches having their actuating coils connected acrossthe armature of said motor and arranged to operate successively as thecounter electromotive force of the motor increases, and a'relay.arranged to interrupt the cire'nit through the actuating coil of thelast switch while the counter electromotive force is more than 'acertain amount below the potential at the source.

6. In'combination, a source of current supply, a motor connectedthereto, a resistance in series with said motor, electro-magneticswitches having their actuating coils connected across the' armature ofsaid motor .and arranged to successively operate as the counterelectromotive force of the motor increases, anda relay having itsactuating coil connected across said resistance and its 0011'- tactsarranged to interrupt the circuit through the actuating coil of the lastelectro-magnetic switch while the voltage at the source is more than acertain amount above the counter electromotive force of the motor. I

7 In combination, a source of current supply, a shunt motor connectedthereto, a resistance in series with the armature of said motor,electro-magnetic switches having their actuating coils connected acrossthe armature of said motor and arranged to opcrate successively as thecounter-electromotlve force of the motor increases, and a relay havingits actuating coil connected across said resistance and its-contactsarranged to interrupt the circuit through the actuating coil of the lastelectro-magnetic switch while the counter electromotive force of themotor is more than a certain amount below the potential at the source.

In witness whereof, I have hereunto set w my hand this 10th day ofSeptember, 1907. MAX R. HANNA.

Witnesses:

BENJAMIN 'B. I-1ULL, MARGARET E. WOOLLEY.

